This invention generally relates to a gas turbine engine, and more particularly to an abradable component for a gas turbine engine.
Gas turbine engines typically include a compressor section, a combustor section and a turbine section. Air is pressurized in the compressor section and is mixed with fuel and burned in the combustor section to add energy to expand the air and accelerate the airflow into the turbine section. The hot combustion gases that exit the combustor section flow downstream through the turbine section, which extracts kinetic energy from the expanding gases and converts the energy into shaft horsepower to drive the compressor section.
The compressor section of the gas turbine engine typically includes multiple compression stages to obtain high pressure levels. Each compressor stage consists of a row of stationary airfoils called stator vanes followed by a row of moving airflows called rotor blades. The stator vanes direct incoming airflow for the next set of rotor blades.
Gas turbine engine operation and efficiency is affected by a number of factors which include component design, manufacturing tolerance, engine clearances and rub interactions. Cantilevered compressor stator vanes are known which are attached at their radial outward end (i.e., the stator vanes are mounted at an end adjacent to the engine casing). A radial inward end of each stator is unsupported and is positioned adjacent to a rotor seal land extending between adjacent rotor stages.
Attempts have been made to decrease the amount of clearance between the tips of the cantilevered stator vanes and the rotor seal lands. For example, cantilevered stator vanes are known in which stator tips rub against an abrasive section inlaid in the rotor seal land during initial running of the engine such that the build clearance between the stator vanes and the rotor seal lands are chosen accordingly. Typically, a build clearance of at least approximately 0.005″ is established between the two components. Thus, the build clearance is such that the rotor seal lands only contact the tips of the stator vanes during the maximum closure point in the flight cycle (i.e., the point of a flight cycle where the rotor blades and the stator vanes experience maximum growth as a result of thermal expansion). Therefore, during a majority of the flight cycle, airflow escapes between the stator vanes and the rotor seal lands and may recirculate resulting in inefficiency and instability of the gas turbine engine. Further, during the initial running of the engine, excessive rub interaction between the stator vanes and the abrasive section of the rotor seal land may result in vane tip damage, mushrooming, metal transfer to adjacent rotors, and rotor burn through.
Accordingly, it is desirable to provide improved rub interaction between adjacent components of a gas turbine engine having a reduced clearance defined therebetween to improve engine efficiency and stability.